1. Field of the Invention
The present invention relates to battery charging circuitry, and more specifically, to modulation charging circuitry for battery charging while reducing thermal emissions.
2. Description of the Related Art
Conventional battery charging circuits typically includes a battery charger IC (Integrated Circuit) that regulates the charging of the battery from a DC (direct current) power source. A conventional battery charger IC includes a switch that couples or decouples the DC power source to/from the battery. When the switch is on, the power source is coupled to the battery thereby charging the battery. When the switch is off, the power source is decoupled from the battery and thus the battery is not charged.
Conventional battery charger ICs typically receive a chip enable (CE) signal to enable or disable the battery charger IC. By keeping the CE signal asserted (either active high or active low), conventional battery charger ICs keep the switch turned on continuously while charging the battery. Thus conventional battery charger ICs require the CE signal to be maintained continuously while the battery is being charged. The CE signal is not asserted only when the battery is not being charged. For example, the conventional battery charger ICs turn the switch off when the battery is fully charged and thus no longer needs charging.
Since the turned-on switch has a small resistance (e.g., 0.2 ohm), the switch generates heat when the battery is charged. When the battery charger IC draws large amounts of current from a high current DC power adaptor, the heat generated by the switch in the battery charger ICs can cause thermal emissions which may be undesirable especially in small portable electronic devices with small size enclosures. The increase in thermal emissions leads to thermal stress on electronic components, which ultimately damages them or can lead to improper operation resulting in data loss or corruption.
Therefore, there is a need for circuitry and a method for charging batteries using a battery charger IC while preventing excessive thermal emissions.